The present invention is related to the field of detecting leaks from small, enclosed volumes and, more particularly, to means and methods for detecting leaks in an integrated circuit package by sealing a micromachined-thermal-convection accelerometer in the integrated circuit package.
Sealed integrated circuit (IC) packages are routinely inspected or testing for leakage. A common test for fine leaks is the helium mass spectrometer test (MIL-STD-883) by which an IC package is stored for a pre-determined period of time (tb) under a pre-determined positive pressure (pw) of helium (He) gas. If there are any leaks, the positive pressure will force the He gas into the “sealed” IC package. Subsequently, the IC package is placed in a He mass spectrometer. If any He gas were forced into the IC package, it will leak out into the He mass spectrometer absent any positive pressure. The He mass spectrometer can generally detect “fine” leakage rates in a range between 10−9 and 10−5 atm-cc/sec.
For “gross” leaks, which by definition are leaks having leakage rates that exceed 10−5 atm-cc/sec, a “bubble test” is common. In conventional “bubble testing”, initially, efforts are made to force a first fluid into any leaks in a “sealed” IC package. Subsequently, the IC package is submerged into a second fluid such as a hot liquid, e.g., fluorocarbon. Leakage from the IC package manifests visually as the first fluid will form gaseous bubbles that out gas from any leaks in the “sealed” IC package.
Alternatively, for “gross” leaks, a residual gas analysis can be performed on the IC package. However, such analyses are destructive and not favored.
Although the above techniques known to the art have their applications, they are unsuitable for testing for leaks or for the leakage rate of an enclosed volume that is smaller than approximately 0.1 cc. Accordingly, it would be desirable to provide means and methods for detecting leaks and/or a leakage rate of an enclosed volume of an IC package that is smaller than approximately 0.1 cc.